It has been known in the art to introduce fluorines on the 26 and 27 carbon atom in certain vitamin D.sub.3 metabolites in order to enhance vitamin D like activity. Thus, for example, U.S. Pat. No. 4,358,406 describes 26,26,26,27,27,27-hexafluoro-1.alpha.,25-dihydroxycholecalciferols which are indicated to have greater vitamin D-like activity compared to the analogous unfluorinated compounds. The compounds of the patent are indicated to be useful in human and veterinary medicine for treatment of calcium and phosphorus deficiency or imbalance. These compounds are thus useful in the treatment of hypoparathyroidism, pseudohypoparathyroidism, renal osteodystrophy, osteoporosis and other bone disorders symptomatic of calcium and phosphorus imbalance. Veterinary applications include, for example, treatment of milk fever in cattle, leg weakness in turkeys, chickens and other domestic animals. Indicated therapeutic dosages for the above indications ranged from 0.1 to micrograms/day orally or parenterally.
In U.S. Pat. No. 4,298,791 there is disclosed 25-hydroxy-26,26,26,27,27,27-hexafluorocholecalciferol. This compound is indicated to have excellent vitamin D.sub.3 -like activity as measured by ability to stimulate calcium transport in the intestine and to mobilize calcium from bone and in its antirachitic activity. Thus the compound is useful in treatment of disease resulting from calcium metabolism disorder.
Kobayashi et al., Tetrahedron Letters, 22 (No 43), 4309 (1981) describe the synthesis of 26,26,26-trifluoro-25-hydroxyvitamin D.sub.3 and 27-nor-26,26,26-trifluoro-25-hydroxyvitamin D.sub.3. No biological activity was reported although the purpose of synthesis was to compare boneresolving activity with the previously described hexafluoro analogs of vitamin D.sub.3.